Some Cornish nationalists have asserted that the stannary law and institutions of Cornwall and Devon predate the Roman conquest of Britain in 43 CE, although it is more likely that stannary law (as a part of the English legal code) emerged in the twelfth century as an attempt to codify the existing customs relating to tin mining and was therefore influenced by Celtic, Anglo-Saxon and Norman practices.

From the perspective of English law, no special administrative arrangements were made for the stannaries before 1198, which suggests that litigation in respect of the mines was brought in the ordinary hundred and shire courts of Devon and Cornwall.

In November 1197, William de Wrotham was appointed to 'act in all matters concerning the King in the stannaries,' and in January 1198, Hubert Walter, the justicar and chief minister to King Richard I, issued a writ convening juries of tinners 'who are better informed about the truth of the matter' before de Wrotham at Exeter and Launceston to declare the law and practice relating to tin coinage.

In addition to establishing the predecessor to the Convocations and the Courts, Walter’s writ also confirmed the 'just and ancient customs and liberties' of the tinners and appointed de Wrotham as the Lord Warden of the Stannaries.

Although their description as jurates suggests that their function was restricted to clarifying the existing law, as they were called upon to do under de Wrotham in 1198, they described themselves as a 'parliament' and their enactments contained new provisions based on an ordinance of Prince Arthur in Cornwall.